The present invention relates to a method for generating a condition value for a measuring point on a machine having a measuring point, and a system for performing the method.
Machines with moving parts are subject to wear with the passage of time, which often causes the condition of the machine to deteriorate. Examples of such machines with movable parts are motors, pumps, generators, compressors, lathes and CNC-machines. It is known to, more or less regularly, investigate the operating condition of such machines. The operating condition can be determined by measuring the amplitude of vibrations in the bearings and by measuring temperature changes on the casing of the machine, which temperatures are dependent on the operating condition of the bearing. Such condition checks of machines with rotating or other moving parts are of great significance for safety and also for the length of the life of such machines. It is known to perform such measurements on machines completely manually. This ordinarily is done by an operator with the help of a measuring instrument performing measurements at a number of measuring points on a machine. The measuring data obtained by means of the measuring instrument for each measuring point is noted down on a pre-printed formula. For a machine it can be necessary to have a number of measuring points in order to later be able to determine the overall operating condition of the machine. For example, three measuring points are often used for the measurement of vibrations of a motor, in such a way that the vibrations are measured in three mutually perpendicular directions, i.e. in the X-direction, in the Y-direction and in the Z-direction. The operator must note down each measured value on the formula. It is furthermore necessary for the operator to evaluate the measured values so that he can make a judgement on whether the measured amplitude measurement values indicate a change for a measuring position so that the machine can be serviced if the measured values indicate wear. This places a large demand on the professional knowledge of the service personnel of which vibration and temperature measurement values are acceptable and which measurement values are not acceptable.
In order to identify damage to bearings it is known to use a shock pulse measuring apparatus by means of which damage to bearings can be determined in machines with rotating machine parts. In order to perform such measurements at a measuring point, the diameter of the shaft and the rotational speed of the shaft are set on a measuring scale. These values, which are set by hand, function as a reference level. If the measured values measured by means of the measuring instrument are greater than the reference level, this can be indicated by means of a warning lamp or by means of a sound signal.
It is known from EP-0 194 333 to provide each measuring point with identity data which is automatically readable by means of a separate reading probe. EP-0 194 333 also describes that the characteristic data values for the measuring point are readable at the measuring point so that the above described reference value can be generated automatically. The reference value is consequently calculated in a standardized and unambiguous way from the characteristic data values. Consequently, according to this known technique, the one and the same reference value is valid for all bearings with a certain shaft diameter and a certain rotational speed.
EP-0 211 212 describes a measuring instrument for detecting and evaluating data representative of the condition of a machine. The described measuring instrument has a measuring probe which is combined with a sensor probe for reading a measuring point code, whereby the measuring probe and the code sensing probe are provided in a common mobile casing.
The problem which is to be solved by means of the present invention is to provide a method which permits an increased accuracy in detecting changes of the condition of a machine.
This problem is solved according to the invention by means of a method for evaluating the condition of a machine with a measuring point, which method is performed by a movable analysis apparatus comprising the steps of:
producing a condition value, by means of a measurement at the measuring point, which condition value is dependent on the current condition of the machine; and
storing the condition value in a writable information carrier (120) which is placed on, or in the vicinity of, the measuring point 90 so that the condition value subsequently can be used as a reference condition value.
According to a preferred embodiment, the reference condition value is produced depending on a measured value, such as a vibration measured value measured in connection with the final inspection of a newly manufactured machine, and on relevant interpreting information, such as shaft diameters and rotational speeds for a rotatable shaft on a machine. With the object of providing a determination of whether some measurable condition change is present, a method according to the invention is performed which comprises the steps of:
a) producing a condition value, which condition value depends upon the actual condition of the machine at the measuring point; and of
b) acquiring a reference value, indicating the condition of the machine at the measuring point at an earlier time point, from an information carrier which is placed by, or in the vicinity of, the measuring point.